NEW ORLEANS — A cold, gray day greeted revelers — but didn’t deter them — along parade routes Tuesday as the Carnival season in New Orleans headed to a crest with the unabashed celebration of Mardi Gras.

The first street marching groups, including clarinetist Pete Fountain’s Half-Fast Walking Club, were to begin their marches along oak-lined St. Charles Avenue and into the business district.

The Zulu parade began on schedule, led by a New Orleans police vanguard on horseback that included Mayor Mitch Landrieu.

Later, the floats of Rex — the king of Carnival — and hundreds of truck trailers decorated by family and social groups would wind down St. Charles Avenue.

Rain fell, and umbrellas and raincoats sprouted along the parade route. Sleet was falling on some merrymakers in areas north and west of the city.

But revelers gathered by the thousands in the French Quarter, where the bawdy side of Mardi Gras would surely be on full display.

Mark Nelson of St. Louis said he would be in the mix even in a downpour for his first Mardi Gras.

“That’s why God made washing machines,” Nelson said as he sipped on a daiquiri.

Revelers lined up near a stand on Bourbon Street where artist Gail Vertucci was painting Carnival masks on faces.

“These people are crazy,” she said. “They’ll get painted no matter what. It doesn’t matter if it’s pouring rain, these people will line up all day long.”

Die-hards braved the weather in costume in the Quarter.

The weather wasn’t going to stop them.

“We’ll drink, drink, drink until it gets drier,” said Dean Cook of New Orleans as he walked Bourbon Street dressed as a pirate with vampire fangs.

“Mermaids love the water,” he said of his wife, Terrina Cook, who was dressed in a shiny blue mermaid costume, complete with a fin.

Along the Uptown parade route, Carol LeBlanc and husband Hov LeBlanc of New Orleans were strolling along St. Charles Avenue with friends Vicki and Duane O'Flynn from Arabi, La. The troupe was dressed as scarecrows, stuffed with grass and wearing plaid pants and tattered coveralls.

Nearby, April Womack and her family had tents set up. Grills were fired up, and pots of crawfish were boiling. They camped overnight, a family tradition for almost two decades. “It’s all about location,” she said.

Her cousin, Yolanda Moton, said Mardi Gras is the opportunity for an annual family reunion, with relatives coming from as far away as Georgia. “This is the one time of the year that everyone in the family fits this in their schedule.”

Sue and Kevin Preece from Edmonton, Canada, were at their first Mardi Gras.

“We wanted to come for Mardi Gras for about 10 years. It was on my bucket list, and he (Kevin) made it happen,” said Sue Preece, a social worker.

Ronnie Davis, a professor of economics at the University of New Orleans, decided to break his button-down image for at least one day. Clad in tutus, he and his wife, Arthurine, strolled through a rain-thinned crowd.

“All year I have to dress professionally. This is the one time I get to act like a fool,” Davis said.

Celebrations were scheduled throughout south Louisiana and in coastal Mississippi and Alabama, sharing the traditions brought by French colonists in the 18th century.

In Louisiana’s bayou parishes, riders on horseback would go from town to town, making merry in what is called the Courir du Mardi Gras.

The merriment must come to a halt at midnight, when the solemn season of Lent begins. New Orleans police were expected to sweep down Bourbon Street at midnight in the annual ritual of letting revelers know the party is over for another year.

The Zulu krewe’s 2014 Witch Doctor, Derek Rabb, said he was charged with praying for the krewe’s good health and good weather on Mardi Gras. “By God’s grace, there will be sun,” he said.

When out of costume, Rabb works at New Orleans-based Entergy Corp. A member of the organization for the past eight years, he said being in such a high-profile position has been an experience he won’t soon forget.

“It’s been a whole lot of fun,” he said. “It’s allowed me to meet some really interesting people.”

Kitty Jensen, of Washington, D.C., said she and about 15 others from the nation’s capital were part of the Kilt of Many Colors and were scheduled to march in the Rex parade.

“We are the party that never ends,” said Jensen, dressed in an airy, royal purple ball gown, reminiscent of the Renaissance era.